Numerous devices such as batteries, fuel cells, electrical interconnects and others can benefit from tightly spaced interdigitated stripes of dissimilar materials. The term ‘stripe’ as used here means a line or other shape of material that contains only that material. It does not mix with adjacent stripes of other materials.
Issues arise when trying to produce tightly spaced interdigitated stripes. In one approach, flow focusing compression produces fine features of functional material in paste form. Examples of this approach can be found in U.S. Pat. No. 7,765,949, issued Aug. 3, 2010; and U.S. Pat. No. 7,799,371, issued Sep. 21, 2010. The approach taken in these patents relates to combining materials into ‘co-laminar’ flows, where three laminar flows of two different materials are brought together to form one flow, but where the two materials do not mix together. This approach suffices in application where the features are on the order of tens of microns arrayed on a millimeter scale pitch. For example, a solar cell may have a width of 156 mm and about 80 gridlines, each about 50 microns wide separated by almost 2 mm from a neighboring gridline.
In contrast, the interdigitated structures called for in the design of electrodes for energy storage devices may require micron scale features interleaved on the micron scale. For example, a typical cathode structure may involve interleaved structures that are 5 microns wide and 100 microns tall. An electrode structure may be 300 mm wide and 60,000 interleaved fingers of dissimilar materials. To dispense these materials from separate nozzles or in from multi-material slot containers would be impractical.